Hello !
Make sure that the calendar has not been unchecked (the checkboxes are located on the left side of the Outlook window).
If you cannot see your calendar, you might have to subscribe to your Google Calendar again. Here's a Microsoft support article on how to do so : https://support.microsoft.com/en-us/office/see-your-google-calendar-in-outlook-c1dab514-0ad4-4811-824a-7d02c5e77126?#picktab=classic_outlook
Please let me know if you have any other question !